Interpolation; Controlling Change With Interpolation; Chapter 11: Advanced Animation - Adobe AFTER EFFECTS 7.0 Manual

Chapter 11: Advanced animation

Interpolation

About interpolation
Interpolation is the process of filling in the unknown data between two known values. In digital video and film, this
usually means generating new values between two keyframes. For example, if you want a graphic element (such as a
title) to move fifty pixels across the screen to the left, and you want it to do so in 15 frames, you' d set the position of
the graphic in the first and 15th frames, and mark them both as keyframes. Then the software would complete the
work of interpolating the frames in between to make the movement appear smooth. Because interpolation generates
all the frames in between the two keyframes, interpolation is sometimes called tweening. Interpolation between
keyframes can be used to animate movement, effects, audio levels, image adjustments, transparency, color changes,
and many other visual and auditory elements.
The two most common types of interpolation are linear interpolation and Bezier interpolation.
Creates an evenly-paced change from one keyframe to another, with each in-between frame
Linear interpolation
given an equal share of the changed value. Changes created with linear interpolation start and stop abruptly and
develop at a constant rate between each pair of keyframes.
Allows the rate of change to accelerate or decelerate based on the shape of a Bezier curve, such
Bezier interpolation
as gently picking up speed at the first keyframe and then slowly decelerating into the second.

Controlling change with interpolation

After you create your keyframes and motion paths to change values over time, you may want to make more precise
adjustments to the way that change occurs. After Effects provides several interpolation methods that affect how
change occurs through and between keyframes. For example, if you are setting up motion, you can choose to make
a layer change direction abruptly or smoothly through a curve. After Effects interpolates values for a change using
the values of the keyframes on both ends of the change.
You can control interpolation between keyframe values over time for all layer properties. For layer properties that
involve movement, such as Position, Anchor Point, Effect Point, and 3D Orientation, you can also control interpo-
lation between motion-path keyframes through space.
Using different interpolation methods, you can specify how the keyframes for each layer property interact with each
other in a composition. For example, when creating a motion path, you can make a layer decelerate as it drifts from
the first keyframe to the second, and then make it quickly bounce off a third keyframe as it rounds a curve and speeds
toward the final keyframe. In addition, you can time-stretch and time-remap layers, and you can use the value and
speed graphs to fine-tune animation.
When you make a layer property vary over time, After Effects selects a default graph type to display in the Graph
Editor, based on the property type (temporal or spatial). For temporal properties, such as Opacity, After Effects
defaults to the value graph. For spatial properties, After Effects displays the interpolated values as a motion path in
the Composition or Layer panel, and by default displays the speed graph in the Graph Editor.
For additional information, go to Adobe Studio on the Adobe website.
Adobe periodically provides updates to software and Help. To check for updates, click the Preferences button
Adobe Help Center, and then click Check For Updates. Follow the on-screen instructions.
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